Thermal destruction and thermophysical properties of polymer composites based on polyester resin with different content of carbon nanotubes

The purpose of this study was to determine the effect of carbon nanotubes (CNTs) on the thermal decomposition and thermo-oxidative destruction of nanocomposites based on polyester resin with a content of 0.1, 0.3 and 0.5 % by weight of CNT as characteristics of their heat resistance. Determination of thermal decomposition products, activation energy of their desorption, total amount of volatile decomposition products of composites was determined by the method of thermoprogrammed desorption mass spectrometry (TPDMS). Using derivatography methods (Q 1500D), patterns of thermo-oxidative destruction of polymer composites were investigated. It is shown that the addition of 0.1 wt. % CNT in the resin shifts the temperatures of the maximum thermograms (Tm) to higher values, increases the activation energy of desorption of all fragments of destruction products in the range m/z 18–104, compared to the original resin, i.e. this indicates an increase in the thermal stability of this composite. Increasing the CNT content to 0.3, 0.5 % by weight shifts Tm towards lower values, significantly reduces the activation energy of desorption for almost all polymer fragments. If at a content of 0.1 wt. %, CNTs in the polymer matrix are structurally “ordered” according to possible mechanisms, then an increase in the content of CNTs, on the contrary, leads to a reversible effect, due to the relatively large content of CNTs, their insufficient deagglomeration and uneven distribution. Thermo-oxidative degradation of unfilled resin has two characteristic minima at T = 383 °C and 439 °C (endothermic reactions of thermo-oxidative decomposition). The addition of CNTs in the amount of 0.1, 0.3, 0.5 wt. % shifts the temperatures towards higher values. Samples melt up to 385 °C followed by combustion with maximum temperatures at 443 and 534 °C. Probably, the presence of the second peak (534 °С) indicates the possibility of the formation of a certain percentage of a more ordered phase in the polymer. Thermooxidative decomposition of composites is characterized by an increase in the initial temperatures of phase transitions. This is probably due to the presence of a carbon nanofiller in the polymer matrix, which increases the heat capacity and thermal conductivity of the composite, possibly initiating crosslinking centers of free (unbound) polymer chains, which, in turn, causes a decrease in kinetic mobility in the polymer.